Battery

This application is a continuation application of the International Application No. PCT/CN2023/141066, filed on Dec. 22, 2023, which claims priority to Chinese Patent Application No. 202310112712.1, filed on Feb. 14, 2023. All of the aforementioned applications are incorporated herein by reference in their entireties.

The present disclosure relates to the technical field of batteries, and in particular, to a battery with good high-temperature cycling performance and high-temperature storage performance.

Over the past decade, lithium battery technology has made rapid progress. It not only has increasingly high energy density but also excellent cycling performance, thus being widely applied in various mobile electronic products such as mobile phones, laptops, and Bluetooth headphones. It is also increasingly used in power fields such as power tools and electric vehicles. How to further increase the energy density of lithium batteries has become the focus and hotspot of research.

Without major system changes, the increase in battery energy density can be achieved simply by raising the battery voltage. Lithium cobalt oxide is a commonly used high-voltage positive electrode material for large-scale commercialization. Increasing the charging and discharging voltage of batteries not only boosts the platform voltage but also enhances the specific capacity of the positive electrode, thereby increasing the energy density of the battery. However, an increase in battery voltage will intensify the side reactions between the electrolyte solution and the positive and negative electrode interfaces, thereby deteriorating the battery's cycling performance.

To enhance the high-voltage cycling stability of batteries, in addition to adjusting the solvent components in the electrolyte solution, adding additives has become the most commonly used and effective approach. However, as the battery voltage further increases, the strategy of adding additives becomes increasingly difficult to play a sufficient role in stabilizing the high-temperature and high-pressure performance of the battery. Therefore, the development of new and effective positive electrode protection strategies becomes even more important.

To address the issue of significant side reactions between the electrolyte solution and the electrode interface in batteries at high voltages, as well as the obvious deterioration of the battery's high-temperature cycling performance and high-temperature storage performance at high voltages, the present disclosure provides a battery. The battery includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte solution. The additives of the electrolyte solution include tricyanophosphite compounds and alkyl polycyanide compounds. Through the synergistic effect between the areal density of the positive electrode and the additives of the electrolyte solution, a very stable interface film and interface coordination effect can be achieved at the positive electrode, significantly enhancing the stability of the interface between the electrolyte solution and the positive electrode. Reduce the consumption of electrolyte solution and the damage to the positive electrode structure during battery cycling, significantly improving the battery's high-temperature cycling performance and high-temperature storage performance at high voltages.

The purpose of the present disclosure is achieved through the following technical solution.

A battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte solution. The electrolyte solution includes a lithium salt, an organic solvent, a first additive that includes a tricyanophosphite compound, and a second additive that includes an alkyl polycyanide compound.

The battery satisfies the following relationship: A≥B/10, where A is a total mass percentage of the first additive and the second additive in the total mass of the electrolyte solution; B is the areal density of the positive electrode, in units of mg/cm.

The beneficial effects of the present disclosure are as follows.

The present disclosure provides a battery, which includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte solution. The additives of the electrolyte solution include a tricyanophosphite compound and an alkyl polycyanide compound. The battery can solve the problem of large side reactions between the electrolyte solution and the electrode interface under high voltage, and the significant deterioration of high-temperature cycling performance and high-temperature storage performance of the battery under high voltage.

The following will further illustrate the technical solutions of the present disclosure in detail with specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present disclosure and should not be construed as limiting the scope of protection of the present disclosure. Any technology realized based on the above content of the present disclosure is covered within the scope of protection intended by the present disclosure.

The experimental methods used in the following embodiments are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following embodiments can be obtained commercially unless otherwise specified.

In the description of the present disclosure, it should be noted that the terms ‘first’, ‘second’, etc. are used for descriptive purposes only and are not intended to indicate or imply relative importance.

The present disclosure provides a battery, including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte solution. The electrolyte solution includes a lithium salt, an organic solvent, a first additive, and a second additive. The first additive includes a tricyanophosphite compound, and the second additive includes an alkyl polycyanide compound.

The battery satisfies the following relationship: A≥B/10, where A is a total mass percentage of the first additive and the second additive in the total mass of the electrolyte solution; B is the areal density of the positive electrode, in units of mg/cm.

In the present disclosure, when calculating the parameters involved in the relationship, only the numerical values are calculated, and their units are not considered. For example, when the total mass of the first additive and the second additive accounts for 0.5% of the total mass of the electrolyte solution, A is 0.5; when the areal density of the positive electrode plate is mg/cm, B is 20.

According to some embodiments of the present disclosure, the first additive includes a tricyanophosphite compound, and the second additive includes an alkyl polycyanide compound.

The two additives can jointly act on the surface of the positive electrode. Specifically, the tricyanophosphite compound contains both a phosphite ester functional group and an alkyl polycyanide functional group. The phosphite ester functional group is easily oxidized on the positive electrode to form a phosphorus-rich dense protective film to protect the positive electrode, while the formed film will bring the alkyl polycyanide functional group to the positive electrode interface. The alkyl polycyanide functional group has a strong coordination effect with the transition metal at the positive electrode interface, which can enhance the protection of the positive electrode and make the formed phosphorus-containing protective film more robust. The simultaneously added alkyl polycyanide compound can further coordinate with the transition metal at weak or broken parts of the film, reducing the oxidation and decomposition of the electrolyte solution at uncovered sites on the positive electrode surface.

The research of this disclosure found that, under the condition that the battery does not show obvious liquid expansion, the higher the areal density B of the positive electrode plate, the higher the content of the positive electrode active material, and the lower the relative content of the electrolyte solution to the positive electrode active material. When the total mass of the first additive and the second additive remains unchanged as a percentage of the total mass of the electrolyte solution, the higher the areal density B of the positive electrode plate, the lower the relative content of the first additive and the second additive to the positive electrode active material. If A<B/10, sufficient positive electrode protection (i.e., phosphorus-containing positive electrode protective film and coordination with the positive electrode transition metal) cannot be formed, which cannot reduce the consumption of the electrolyte solution and the damage to the positive electrode structure during the battery cycle, significantly deteriorating the high-temperature cycling performance and high-temperature storage performance of the battery at high voltage (4.53 V). Therefore, the content of A needs to be increased. When the battery satisfies A≥B/10, the electrolyte additive can form a stable and robust interface protection on the positive electrode surface, and the amount of the electrolyte additive can well match the areal density of the positive electrode, effectively improving the stability of the interface protective film on the positive electrode surface, significantly enhancing the stability of the electrolyte solution and the positive electrode interface, reducing the consumption of the electrolyte solution and the damage to the positive electrode structure during the battery cycle, and significantly improving the high-temperature cycling performance and high-temperature storage performance of the battery at high voltage (4.53 V).

In the present disclosure, A≥B/10, that is, B/A≤10. For example, the ratio of B/A can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any point value within the range composed of the above two-point values.

According to the embodiments of the present disclosure, the battery satisfies the following relationship: A≥3/C, that is, A*C≥3, for example, A*C can be 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or any point value within the range composed of the above two-point values, where A is the total mass of the first additive and the second additive as a percentage of the total mass of the electrolyte solution; C is a liquid retention coefficient of the battery, which is the ratio of the liquid retention mass (g) of the battery to the battery capacity (Ah).

The lower the liquid retention coefficient C of the battery, the lower a liquid retention mass relative to the battery capacity, and thus the lower the liquid retention mass relative to the content of the positive electrode active material. To achieve the same positive electrode protection effect, the proportion of the additive in the electrolyte solution must be increased. Research has found that when A≥3/C, sufficient interface protection can be formed at the positive electrode interface, significantly improving the high-temperature cycle and high-temperature storage performance of the battery at high voltage.

According to the embodiments of the present disclosure, the total mass of the first additive and the second additive accounts for 0.5%-5% of the total mass of the electrolyte solution, that is, A is 0.5-5. For example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 3%, 3.4%, 3.5%, 4%, 4.5%, 4.8%, or 5%, or any point value within the range composed of the above two-point values. When the mass ratio of the first additive and the second additive is within the above range, it is beneficial for the electrolyte additive to form a more stable and robust protective layer on the positive electrode surface, significantly enhancing the stability of the electrolyte solution and the positive electrode interface, and effectively improving the high-temperature cycling performance and high-temperature storage performance of the battery under high voltage.

According to an embodiment of the present disclosure, the areal density of the positive electrode plate is 5 mg/cm-30 mg/cm, that is, B is 5 to 30. For example, it can be 5 mg/cm, 6 mg/cm, 7 mg/cm, 8 mg/cm, 9 mg/cm, 10 mg/cm, 12 mg/cm, 13 mg/cm, 15 mg/cm, 18 mg/cm, 20 mg/cm, 22 mg/cm, 23 mg/cm, 24 mg/cm, 25 mg/cm, 26 mg/cm, 28 mg/cm, or 30 mg/cm, or any point value within the range composed of the above two-point values. In some embodiments, if the areal density of the positive electrode plate is too high (e.g., greater than 30 mg/cm), the positive electrode plate will be too thick, resulting in poor kinetic performance of the battery and inability to charge and discharge normally. If the areal density of the positive electrode plate is too low (e.g., less than 5 mg/cm), the overall energy density of the battery will be too low to meet disclosure requirements.

According to an embodiment of the present disclosure, the liquid retention coefficient C is 1 g/Ah-2 g/Ah, that is, C is 1 to 2. For example, it can be 1.0 g/Ah, 1.1 g/Ah, 1.2 g/Ah, 1.3 g/Ah, 1.4 g/Ah, 1.5 g/Ah, 1.6 g/Ah, 1.7 g/Ah, 1.8 g/Ah, 1.9 g/Ah, 2.0 g/Ah, or any point value within the range composed of the above two-point values. If the liquid retention coefficient is too low, the electrolyte solution content (battery liquid retention mass) will be too small, significantly deteriorating the battery cycling performance. If the liquid retention coefficient is too high, the energy density of the battery will be too low to meet practical disclosure requirements. A simple test method for the liquid retention coefficient is as follows: charge the cell to the cut-off voltage at 0.2C, then discharge it to the cut-off voltage at 0.2C to obtain the cell capacity DC. Weigh the entire cell as G1, then disassemble the cell, soak the disassembled cell in a large amount of DMC (dimethyl carbonate), fully dry the soaked cell, and weigh it as G2. The liquid retention coefficient is (G1−G2)/DC.

According to the embodiments of the present disclosure, the battery satisfies the following relationship: 2A/3≥X≥A/5, that is, 1/5≤X/A≤2/3 (X/A can be 0.2, 0.24, 0.28, 0.32, 0.36, 0.4, 0.44, 0.48, 0.52, 0.56, 0.6, 0.64, etc.), where X is the mass percentage of the tricyanophosphite compound in the total mass of the electrolyte solution.

According to an embodiment of the present disclosure, when the battery satisfies 2A/3≥X≥A/5, the tricyanophosphite compound and the alkyl polycyanide compound in the electrolyte solution can better exert a synergistic effect, forming a sufficiently robust and stable protective layer.

According to the embodiments of the present disclosure, the battery satisfies the following relationship: Y=A−X, where Y is the mass percentage of the alkyl polycyanide compound in the total mass of the electrolyte solution.

According to an embodiment of the present disclosure, the mass percentage X of the tricyanophosphite compound in the total mass of the electrolyte solution is 0.1%-3.3%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, or 3.3%, or any point value within the range composed of the above two-point values, preferably 0.5%-2.5%. The preferred mass proportion of the tricyanophosphite compound can further enhance the protection of the positive electrode, improving the high-temperature cycling performance and high-temperature storage performance of the battery under high voltage.

According to an embodiment of the present disclosure, the tricyanophosphite compound has the structural formula shown in Formula (1):

In Formula (1), R, R, and Rare independently selected from unsubstituted or optionally substituted (with one, two, or more Ra groups) Calkylene, Carylene, or —Calkylene-C(═O)—O—Calkylene-, where each Ris independently selected from halogen, or Calkyl.

That is, in Formula (1), R, R, and Rare independently selected from substituted or unsubstituted Calkylene, substituted or unsubstituted Carylene, or substituted or unsubstituted —Calkylene-C(═O)—O—Calkylene-, where the substituent is R, and each Ris independently selected from halogen, or Calkyl.

According to an embodiment of the present disclosure, in Formula (1), R, R, and Rare independently selected from unsubstituted or optionally substituted Calkylene, Carylene, or —Calkylene-C(═O)—O—Calkylene-, where each Ris independently selected from halogen or Calkyl. That is, in Formula (1), R, R, and Rare independently selected from substituted or unsubstituted Calkylene, substituted or unsubstituted Carylene, or, substituted or unsubstituted —Calkylene-C(═O)—O—Calkylene-, where the substituent is R, and each Ris independently selected from halogen or Calkyl.

According to the embodiments of the present disclosure, in formula (1), R, R, and Rare independently selected from unsubstituted or optionally substituted Calkylene, phenylene, or —C1-3 alkylene-C(═O)—O—Calkylene-, each Ris independently selected from halogen, or Calkyl. That is, in formula (1), R, R, and Rare independently selected from substituted or unsubstituted Calkylene, substituted or unsubstituted phenylene, or substituted or unsubstituted —Calkylene-C(═O)—O—Calkylene-, the substituent being R, each Ris independently selected from halogen, or Calkyl.

According to the embodiments of the present disclosure, in formula (1), R, R, and Rare independently selected from substituted or unsubstituted —CH—, substituted or unsubstituted —CHCH—, substituted or unsubstituted —CHCHCH—, substituted or unsubstituted —CHCH(CH)—, substituted or unsubstituted ortho-phenylene, substituted or unsubstituted meta-phenylene, substituted or unsubstituted para-phenylene, substituted or unsubstituted —CH—C(═O)—O—CH—, or substituted or unsubstituted —CHCH—C(═O)—O—CHCH—, where the substituent is R, and each Ris independently selected from F, —CH, —CHCH, —CHCHCH, or —CH(CH)CH.

According to the embodiments of the present disclosure, the tricyanophosphite compound includes at least one of the compounds shown in formulas (2) to (9).

According to the embodiments of the present disclosure, the tricyanophosphite compound can be obtained through commercial channels or prepared using methods known in the art.

According to the embodiments of the present disclosure, the alkyl polycyanide compound has the chemical formula shown in formula (10):

In formula (10), R is an alkyl group, and n is an integer greater than or equal to 3.

According to the embodiments of the present disclosure, in formula (10), R is C3-8 alkyl, such as n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, or their isomeric groups.

According to the embodiments of the present disclosure, in formula (10), n is 3 or 4. When n is 3 or 4, the alkyl polycyanide compounds are tricyano compounds or tetracyano compounds, which can provide more cyano functional groups, further enhance the coordination between the alkyl polycyanide compounds and transition metals at the positive electrode interface, strengthen the protection of the positive electrode, and further reduce the oxidation and decomposition of the electrolyte solution at uncovered sites on the positive electrode surface.

According to the embodiments of the present disclosure, the alkyl polycyanide compound includes at least one of 1,3,6-hexanetricarbonitrile (HTCN, NC(CH)CH(CN)CHCHCN), 1,2,3-propanetricarbonitrile, or 1,2,2,3-tetracyanopropane.

According to the embodiments of the present disclosure, the alkyl polycyanide compound can be obtained through commercial channels or prepared using methods known in the art.

According to the embodiments of the present disclosure, the electrolyte solution further includes a third additive, and the third additive includes at least one of adiponitrile (ADN), succinonitrile, fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), or 1,3-propene sultone.

According to the embodiments of the present disclosure, the weight of the third additive is 0 wt %-15 wt % of the total weight of the electrolyte solution, such as 0.5 wt %, 1 wt %, 1.5 wt %, 2 wt %, 2.5 wt %, 3 wt %, 3.5 wt %, 4 wt %, 4.5 wt %, 5 wt %, 5.5 wt %, 6 wt %, 6.5 wt %, 7 wt %, 7.5 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, or 15 wt %, or any point value within the range formed by the above two-point values. Under the combined action of the third additive with the first and second additives, both the positive electrode and negative electrode can be protected simultaneously, improving the high-temperature cycling performance and high-temperature storage performance of the battery at high voltage.

According to the embodiments of the present disclosure, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF), lithium difluorophosphate (LiPOF), lithium difluorooxalatoborate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(oxalato)phosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(pentafluoroethanesulfonyl)imide, lithium tris(trifluoromethanesulfonyl)methide, or lithium bis(trifluoromethanesulfonyl)imide.